Sulphur is included in many coals which makes those coals undesirable for use without expensive and efficiency reducing equipment to recover the products of sulphur combustion. One of the products of combustion of sulphur containing coals is sulphur dioxide, which is considered to be a highly undesirable pollutant of the atmosphere. It is generally recognized that sulphur in coal is present in a variety of forms. There are three basic forms, namely; pyritic sulphur, a sulphate, and organic sulphur. The pyritic sulphur is sulphur combined with iron. The sulphate sulphur is generally of a minute quantity, that is, it usually constitutes 1% or 2% of all the sulphur in a given coal specimen. Organic sulphur is sulphur which is combined in an organic compound with the carbon of the coal.
Organic sulphur is generally found to be difficult to remove from coal in that organic sulphur and compounds of coal are not well-defined. The problem which confronts most investigators is how to remove organic sulphur from coal. U.S. Letters Pat. No. 4,233,034 issued Nov. 11, 1980, to Miller et al. entitled "Desulfurization of Coal". The Miller et al patent discloses a process for removing sulphur from coal. The process taught in the Miller et al patent does not distinguish between the removal of organic sulphur from the removal of pyritic sulphur, but the teaching is simply directed to a process of removing sulphur without distinction of what type of sulphur is removed. It is known to remove pyritic sulphur efficiently from coal. The problem revolves around removing the organic sulphur efficiently.